1. Field of the Invention
The present invention relates to display devices in general and more particularly to display devices capable of preventing the disconnection of data lines resulting from irregular side edges of gate lines.
2. Description of the Related Art
A typical liquid crystal display (LCD) includes the following components: a TFT substrate in which pixel electrodes and thin film transistors (TFTs) are arranged in the form of a matrix; a counter substrate that faces the TFT substrate and includes color filters that face the pixel electrodes of the TFT substrate; and a liquid crystal panel placed between the TFT substrate and the counter substrate. Such a LCD produces an image by controlling the light transmittance of the liquid crystal molecules on a pixel-by-pixel basis.
Because LCDs are flat and lighter in weight, their application is wide: they are used as large-sized televisions, cell phone displays, DSC (Digital Still Camera) displays, and so on. Although LCDs in general have problems with viewing angles (meaning how an image looks differs depending on the viewing angle), IPS (In-Plane Switching) LCDs offer wider viewing angles.
In a LCD, gate lines extend in a first direction and are arranged in a second direction while data lines extend in the second direction and are arranged in the first direction. Pixels are each formed within one of the regions surrounded by the gate lines and the data lines. The data lines override and thereby traverse the gate lines with an insulating layer deposited therebetween.
When a side edge of a gate line is steep or has a reverse taper, a cross section of an insulating film to be deposited over the gate line becomes irregular. This in turn results in disconnection of a data line to be formed on the insulating film. In relation to this, JP-A-1994-85257 discloses a method of preventing damage to an insulating layer protecting a channel protective layer. To achieve that purpose, the channel protective layer, which covers the channel region of a TFT, is shaped to have two insulating layers. In addition, the etch speed of the upper layer is made larger so that the channel protective layer can have a taper at its side edge.